To meet Federal Motor Vehicle Safety Standards, a vehicle may include an upper anchor attachment to receive a child safety seat tether hook connected to an upper portion of the child safety seat back. The connection of the upper portion of the child safety seat to the vehicle may reduce the forward movement of the child safety seat during a frontal crash. However, shock applied by the child safety seat restraining equipment to the child safety seat occupant may increase in the case of a forward vehicle collision.
One approach to reduce the impact of the collision force to a passenger seat is described in U.S. Pat. No. 3,547,468. In particular, the energy absorbing device includes a generally U-shaped housing having two pins and one bolt extending between the sidewalls of the housing. A double layer of strip metal is coiled to form a supply of strip metal. From the coil, two layers of metal strips are spread by the bolt and then are threaded through two pins. When the strip metal is pulled under a force, the coil is uncoiled and portions of the strip metal are spread apart by a bolt and then are pinched toward one another by the two pins. The bending of the strip portions by the pins and bolt absorbs energy.
However, the inventors herein have recognized disadvantages with such an energy absorbing device. Specifically, since the width and the thickness of the strip metal are constant, the load applied to the child safety seat may be constant as the double layered strips spread around the bolt and are pinched by the two pins, which may not be desired in some situations. Further, the energy absorbing device is heavy and complicated because the device comprises a strip coil, the double layered metal strips, and other components.